Melatonin and glutathione reduce lipid peroxidation products in lymphocytes cultured with H₂O₂ and iron

The protective effect of melatonin against oxidant-induced free radical damage was examined in vitro. Lymphocytes, isolated from rat spleen, were incubated for 60 min with H₂O₂ (5 mM) or FeSO₄ (20 μM), either alone or together with melatonin or glutathione at increasing concentrations from 0.1 to 2 mM. Lymphocytic malonaldehyde (MDA) plus 4-hydroxyalkenals (4-HDA) concentrations were measured as indices of induced membrane peroxidative damage. The level of lipid peroxidation products in lymphocytes increased significantly after the combination of H₂O₂ and FeSO₄; that effect was abolished by both melatonin and glutathione. The inhibitory effect of melatonin on lipid peroxidation was directly correlated with the concentration of the indole in medium. Additionally, the effect of melatonin was compared with that of well-known endogenous antioxidant, glutathione.